Aluminium is extracted from alumina `(Al_(2)O_(3))` by electrolysis of a molten mixture of

Options

A. `Al_(2)O_(3)+HF+NaAlF_(4)`
B. `Al_(2)O_(3)+CaF_(2)+NaAlF_(4)`
C. `Al_(2)O_(3)+Na_(3)AlF_(6)+CaF_(2)`
D. `Al_(2)O_(3)+KF+Na_(3)AlF_(6)`

Answer

C

Explanation

Fused alumina `(Al_(2)O_(3))` is a bad conductor of electrieity. Therefore, cryolite `(Na_(3)AlF_(6))` and fluorspar `(CaF_(2))` are added to purified alumina which not only make alumina a good conductor of electriety but also reduce the melting point of the mixture to around 1140 K.